The structure of the singular set and its spectrum is invariant with respect to the choice of cross-section \(\Delta \) , as well as the choice of local coordinates on \(\Delta \) ; see e.g. [1]}. Thus it suffices to show the result for a particular choice of \(\Delta \) . The derivation of the Poincaré map is similar to derivation in the context 3-dimensional systems in [2]}.
